3,614 research outputs found
Typical orbits of quadratic polynomials with a neutral fixed point: Brjuno type
We describe the topological behavior of typical orbits of complex quadratic
polynomials P_alpha(z)=e^{2\pi i alpha} z+z^2, with alpha of high return type.
Here we prove that for such Brjuno values of alpha the closure of the critical
orbit, which is the measure theoretic attractor of the map, has zero area. Then
combining with Part I of this work, we show that the limit set of the orbit of
a typical point in the Julia set is equal to the closure of the critical orbit.Comment: 38 pages, 5 figures; fixed the issues with processing the figure
A biogenic amine and a neuropeptide act identically: tyramine signals through calcium in drosophila tubule stellate cells
Insect osmoregulation is subject to highly sophisticated endocrine control. In Drosophila, both Drosophila kinin and tyramine act on the Malpighian (renal) tubule stellate cell to activate chloride shunt conductance, and so increase the fluid production rate. Drosophila kinin is known to act through intracellular calcium, but the mode of action of tyramine is not known. Here, we used a transgenically encoded GFP::apoaequorin translational fusion, targeted to either principal or stellate cells under GAL4/UAS control, to demonstrate that tyramine indeed acts to raise calcium in stellate, but not principal cells. Furthermore, the EC(50) tyramine concentration for half-maximal activation of the intracellular calcium signal is the same as that calculated from previously published data on tyramine-induced increase in chloride flux. In addition, tyramine signalling to calcium is markedly reduced in mutants of NorpA (a phospholipase C) and itpr, the inositol trisphosphate receptor gene, which we have previously shown to be necessary for Drosophila kinin signalling. Therefore, tyramine and Drosophila kinin signals converge on phospholipase C, and thence on intracellular calcium; and both act to increase chloride shunt conductance by signalling through itpr. To test this model, we co-applied tyramine and Drosophila kinin, and showed that the calcium signals were neither additive nor synergistic. The two signalling pathways thus represent parallel, independent mechanisms for distinct tissues (nervous and epithelial) to control the same aspect of renal function
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Soft power, hard news:How journalists at state-funded transnational media legitimize their work
How do journalists working for different state-funded international news organizations legitimize their relationship to the governments which support them? In what circumstances might such journalists resist the diplomatic strategies of their funding states? We address these questions through a comparative study of journalists working for international news organizations funded by the Chinese, US, UK and Qatari governments. Using 52 interviews with journalists covering humanitarian issues, we explain how they minimized tensions between their diplomatic role and dominant norms of journalistic autonomy by drawing on three â broadly shared â legitimizing narratives, involving different kinds of boundary-work. In, the first âexclusionaryâ narrative, journalists differentiated their âtruthfulâ news reporting from the âfalseâ state âpropagandaâ of a common Other, the Russian-funded network, RT. In the second âfuzzifyingâ narrative, journalists deployed the ambiguous notion of âsoft powerâ as an ambivalent âboundary conceptâ, to defuse conflicts between journalistic and diplomatic agendas. In the final âinversionâ narrative, journalists argued that, paradoxically, their dependence on funding states gave them greater âoperational autonomyâ. Even when journalists did resist their funding states, this was hidden or partial, and prompted less by journalistsâ concerns about the political effects of their work, than by serious threats to their personal cultural capital
Exact solutions to the four Goldstone modes around a dark soliton of the nonlinear Schroedinger equation
This article is concerned with the linearisation around a dark soliton
solution of the nonlinear Schr\"odinger equation. Crucially, we present
analytic expressions for the four linearly-independent zero eigenvalue
solutions (also known as Goldstone modes) to the linearised problem. These
solutions are then used to construct a Greens matrix which gives the
first-order spatial response due to some perturbation. Finally we apply this
Greens matrix to find the correction to the dark-soliton wavefunction of a
Bose-Einstein condensate in the presence of fluctuations.Comment: 14 pages, 3 figures, submitted to Journal of Physics
White Lines and 3d-Occupancy for the 3d Transition-Metal Oxides
Electron energy-loss spectrometry was employed to measure the white lines at
the L23 absorption edges of the 3d transition-metal oxides and lithium
transition-metal oxides. The white-line ratio (L3/L2) was found to increase
between d^0 and d^5 and decrease between d^5 and d^10, consistent with previous
results for the transition metals and their oxides. The intensities of the
white lines, normalized to the post-edge background, are linear for the 3d
transition-metal oxides and lithium transition-metal oxides. An empirical
correlation between normalized white-line intensity and 3d occupancy is
established. It provides a method for measuring changes in the 3d-state
occupancy. As an example, this empirical relationship is used to measure
changes in the transition-metal valences of Li_{1-x}Ni_{0.8}Co_{0.2}O_2 in the
range of 0 < x < 0.64. In these experiments the 3d occupancy of the nickel ion
decreased upon lithium deintercalation, while the cobalt valence remained
constant.Comment: 6 pages, 7 figure
Amblyraja georgiana, Antarctic Starry Skate
The Antarctic Starry Skate (Amblyraja georgiana) is a medium-sized (to 115 cm total length) deepwater skate that occurs in the Southeast Pacific Ocean off southern Chile, in the Southwest Atlantic Ocean off southern Argentina and the Falkland Islands (Malvinas), in the Atlantic and Pacific Antarctic Oceans from South Georgia Island and the Antarctic Peninsula to the Ross Sea, and in the Indian Antarctic off the Crozet Islands. It is demersal on continental and insular slopes at depths of 20?1,255 m, and is captured as bycatch in trawl and longline fisheries, particularly those targeting Patagonian Toothfish (Dissostichus eleginoides). There are no population size estimates for this skate, and it is not clear what the current population trend is. Although estimates of bycatch around South Georgia and the Ross Sea are comprised of a low percentage of overall estimated stock biomass, the demographic consequences are unknown and require further research. Furthermore, catch levels in other areas are unknown, and some specimens previously referred to as this species may include cryptic individuals of a yet-to-be-described species. Overall, it is not clear what level of fishing mortality this species is exposed to across its range, and further research is needed on distribution, population size and trend, and threats. Therefore, the Antarctic Starry Skate is assessed as Data Deficient.Fil: Pollom, R.. University Fraser Simon; CanadĂĄFil: Acuña, E.. Universidad CatĂłlica del Norte; ChileFil: Bustamante, C.. Universidad de Antofagasta; ChileFil: Chiaramonte, Gustavo Enrique. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia". EstaciĂłn HidrobiolĂłgica de Puerto QuequĂ©n (sede QuequĂ©n); ArgentinaFil: Cuevas, J.M.. Wildlife Conservation Society; Estados UnidosFil: Herman, K.. Georgia Aquarium; Estados UnidosFil: Pompert, J.. No especifĂca;Fil: Velez Zuazo, X.. No especifĂca
Entanglement Evolution in the Presence of Decoherence
The entanglement of two qubits, each defined as an effective two-level, spin
1/2 system, is investigated for the case that the qubits interact via a
Heisenberg XY interaction and are subject to decoherence due to population
relaxation and thermal effects. For zero temperature, the time dependent
concurrence is studied analytically and numerically for some typical initial
states, including a separable (unentangled) initial state. An analytical
formula for non-zero steady state concurrence is found for any initial state,
and optimal parameter values for maximizing steady state concurrence are given.
The steady state concurrence is found analytically to remain non-zero for low,
finite temperatures. We also identify the contributions of global and local
coherence to the steady state entanglement.Comment: 12 pages, 4 figures. The second version of this paper has been
significantly expanded in response to referee comments. The revised
manuscript has been accepted for publication in Journal of Physics
Schroederichthys bivius, Narrowmouth Catshark
The Narrowmouth Catshark (Schroederichthys bivius) is a small (to 82 cm total Length) catshark that occurs in the Southeast Pacific and Southwest Atlantic from Valdivia, Chile, south around Cape Horn and north to southern Brazil. It is demersal on the continental shelf and upper slope at depths of 12-359 m (mostly <130 m). It is occasionally caught as bycatch of industrial and artisanal trawlers in Chile, Uruguay, Argentina, and the Falkland Islands (Malvinas). It is not typically utilized and is usually discarded dead. Overall, this catshark is caught throughout most of its range in small numbers. Its small size and presumably productive life history, combined with a lack of evidence of a population reduction, indicates that it is likely able to withstand limited exposure to fishing pressure. The population is suspected to be stable, therefore, the Narrowmouth Catshark is assessed as Least Concern.Fil: Dulvy, N. K.. University Fraser Simon; CanadĂĄFil: Acuña, E.. Universidad CatĂłlica del Norte; ChileFil: Bustamante, C.. Universidad de Antofagasta; ChileFil: Chiaramonte, Gustavo Enrique. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia". EstaciĂłn HidrobiolĂłgica de Puerto QuequĂ©n (sede QuequĂ©n); ArgentinaFil: Cuevas, J. M.. Wildlife Conservation Society; Estados UnidosFil: Herman, K.. Georgia Aquarium; Estados UnidosFil: Pompert, J.. Georgia Seafoods; PaĂses BajosFil: Velez Zuazo, X.. Smithsonian Conservation Biology Institute; Estados Unido
Ab initio study of the volume dependence of dynamical and thermodynamical properties of silicon
Motivated by the negative thermal expansion observed for silicon between 20 K
and 120 K, we present first an ab initio study of the volume dependence of
interatomic force constants, phonon frequencies of TA(X) and TA(L) modes, and
of the associated mode Gruneisen parameters. The influence of successive
nearest neighbors shells is analysed. Analytical formulas, taking into account
interactions up to second nearest neighbors, are developped for phonon
frequencies of TA(X) and TA(L) modes and the corresponding mode Gruneisen
parameters. We also analyze the volume and pressure dependence of various
thermodynamic properties (specific heat, bulk modulus, thermal expansion), and
point out the effect of the negative mode Gruneisen parameters of the acoustic
branches on these properties. Finally, we present the evolution of the mean
square atomic displacement and of the atomic temperature factor with the
temperature for different volumes, for which the anomalous effects are even
greater.Comment: 24 pages, Revtex 3.0, 11 figures, accepted for publication in Phys.
Rev.
Therapeutic limitations in tumor-specific CD8+ memory T cell engraftment
BACKGROUND: Adoptive immunotherapy with cytotoxic T lymphocytes (CTL) represents an alternative approach to treating solid tumors. Ideally, this would confer long-term protection against tumor. We previously demonstrated that in vitro-generated tumor-specific CTL from the ovalbumin (OVA)-specific OT-I T cell receptor transgenic mouse persisted long after adoptive transfer as memory T cells. When recipient mice were challenged with the OVA-expressing E.G7 thymoma, tumor growth was delayed and sometimes prevented. The reasons for therapeutic failures were not clear. METHODS: OT-I CTL were adoptively transferred to C57BL/6 mice 21 â 28 days prior to tumor challenge. At this time, the donor cells had the phenotypical and functional characteristics of memory CD8+ T cells. Recipients which developed tumor despite adoptive immunotherapy were analyzed to evaluate the reason(s) for therapeutic failure. RESULTS: Dose-response studies demonstrated that the degree of tumor protection was directly proportional to the number of OT-I CTL adoptively transferred. At a low dose of OT-I CTL, therapeutic failure was attributed to insufficient numbers of OT-I T cells that persisted in vivo, rather than mechanisms that actively suppressed or anergized the OT-I T cells. In recipients of high numbers of OT-I CTL, the E.G7 tumor that developed was shown to be resistant to fresh OT-I CTL when examined ex vivo. Furthermore, these same tumor cells no longer secreted a detectable level of OVA. In this case, resistance to immunotherapy was secondary to selection of clones of E.G7 that expressed a lower level of tumor antigen. CONCLUSIONS: Memory engraftment with tumor-specific CTL provides long-term protection against tumor. However, there are several limitations to this immunotherapeutic strategy, especially when targeting a single antigen. This study illustrates the importance of administering large numbers of effectors to engraft sufficiently efficacious immunologic memory. It also demonstrates the importance of targeting several antigens when developing vaccine strategies for cancer
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